Sesamol Derivatives as Novel Inhibitors of Arachidonic Acid Formation

ABSTRACT

The invention relates to a novel class of inhibitor of arachidonic acid useful for treating inflammatory conditions. Specifically, the invention relates to hydrophobic and hydrophilic derivatives of sesamol that confer lower toxicity and increased circulatory lifetimes than pure sesamol.

FIELD OF INVENTION

The invention relates to compositions and methods for treating,moderating, and preventing inflammation. Specifically, the inventionrelates to compositions useful for inhibiting the formation ofarachidonic acids, which are precursors of pro-inflammatory eicosanoids.The invention also relates to methods of preparing and administeringsuch compositions.

BACKGROUND OF THE INVENTION

It is becoming increasingly recognized that increased inflammation isstrongly associated with, if not the underlying cause of, many diseaseconditions including obesity, type 2 diabetes, cancer, heart disease,and neurological conditions such as multiple sclerosis and Alzheimer'sdisease.

It has been shown that the regulation of certain eicosanoids, a class ofbiologically active metabolites, can help control inflammation. Whilemany anti-inflammatory drugs directly target the production ofpro-inflammatory eicosanoids, e.g., by inhibiting the enzyme required intheir production, an alternative and more sophisticated approach wouldbe to reduce the amount of substrate upstream in the pathway, i.e., byregulating the formation of the precursors of pro-inflammatoryeicosanoids, namely arachidonic acid (AA). Since AA is produced by theenzyme Δ-5-desaturase (D5D), the synthesis and/or identification ofspecific inhibitors of D5D can help to treat, moderate, and preventinflammation. U.S. Pat. No. 6,172,106, the entire disclosure of which isincorporated by reference herein, has identified sesamol as a specificinhibitor of D5D. Unfortunately, sesamol is believed to be potentiallytoxic. Additionally, although natural compounds such as sesame lignansand curcumin have been demonstrated to exhibit inhibitory activity onD5D, their complex structures make them difficult to synthesize.Furthermore, sesame lignans also have potential toxicity. Hence, thereis a need to develop non-toxic inhibitors of D5D that are easy tosynthesize and can be produced on an industrial scale.

SUMMARY OF THE INVENTION

It has been discovered that the toxicity of sesamol can be reduced orcompletely eliminated by preparing a carboxylic derivative of sesamolwithout compromising its inhibitory effect on Δ-5-desaturase (D5D).

The invention thus provides compositions comprising a carboxylicderivative of sesamol that are useful as anti-inflammatory agents.Specifically, the derivative is non-toxic, or has a low toxicity thatcan be tolerated by mammals including humans.

In some embodiments, the carboxylic derivative may comprise at least onefatty acid. In other embodiments, the carboxylic derivative may comprisea carboxylic acid derivative of polyethylene oxide, i.e., a polyethyleneoxide with at least one carboxylic acid terminal group. Both types ofderivatives allow sesamol to be released slowly in its active form, thusreducing any potential toxicity of the composition. Such controlledrelease of sesamol also helps to modulate the activity of D5D in a moreconsistent fashion.

The compositions of the invention may be administered to human patientsthat require treatment for conditions associated with inflammation.Exemplary inflammation-associated conditions include, but are notlimited to, obesity, type 2 diabetes, cardiovascular disease, cancer,neurological disorders, as well as any inflammatory conditions thatcause pain. The compositions of the invention also may be administeredto non-human mammals for veterinary purposes.

In another aspect, the invention provides methods for inhibiting theformation of arachidonic acid in a mammal by administering to the mammala composition comprising a non-toxic chemical derivative of sesamol. Thenon-toxic chemical derivative may comprise a carboxylic derivative ofsesamol. In some embodiments, the sesamol may be derivatized with atleast one fatty acid. The at least one fatty acid may have a carbonchain comprising 2 to 22 carbon atoms. Additionally, the at least onefatty acid may have a degree of unsaturation in the range of 0 to 6 perfatty acid molecule. In one embodiment, the non-toxic chemicalderivative is sesamol oleate. In other embodiments, the non-toxicchemical derivative may comprise a carboxylic acid derivative ofpolyethylene oxide. The polyethylene oxide may comprise 2 to 400repeating units.

Yet another aspect of the invention provides methods for moderating aninflammatory response in a mammal by administering to the mammal acomposition comprising a non-toxic chemical derivative of sesamol. Thenon-toxic chemical derivative may include the embodiments describedabove. The composition may be administered via an enteral or parenteralroute, and may comprise other biologically acceptable carriers,excipients, or diluents. Supplementary active ingredients also may beincorporated into the composition. The composition may be administeredas a nutritional supplement, and may be prepared in various formsincluding, but not limited to, a capsule, a bar, a tablet, a powder, ora beverage package.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 illustrates the metabolic pathways leading to the production ofpro-inflammatory eicosanoids.

FIG. 2 shows the chemical structures of two embodiments of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1, the enzyme Δ-5-desaturase (D5D) is required forconverting dihomo gamma linolenic acid (DGLA) into arachidonic acid(AA). Thus, being able to control the activity of D5D via a suitableinhibitor can significantly reduce the production of AA, which in turnreduces the supply of the substrate required to generatepro-inflammatory eicosanoids.

Sesamol is a chemical compound that has been shown to inhibit D5Dactivity. However, sesamol is believed to be potentially toxic. Theapplicant has discovered that the toxicity of sesamol can besignificantly reduced by acylating the free hydroxyl group of sesamolwith a suitable carboxylic acid moiety, including fatty acids andcarboxylic derivatives of polyethylene oxide. FIG. 2 shows the chemicalstructures of two sesamol compounds derivatized with a generic fattyacid (compound Ia) and a carboxylic acid derivative of methoxypolyethylene oxide (compound Ib), respectively. The variables m and nmay be an integer in the range of 1 to 11, and 2 to 400, respectively.Such derivatization also helps to enhance the stability andbioavailability of the sesamol compound by attaching it to abiologically inert hydrophilic (i.e., polyethylene oxide) or hydrophobic(i.e., fatty acid) moiety.

Fatty acid derivatives of sesamol may be prepared from various fattyacids. Natural fatty acids, either isolated from natural sources or madesynthetically, are preferred. Both saturated fatty acids and fatty acidswith various degrees of unsaturation may be used, depending on thephysical properties that one desires to impart to the invention. Forinstance, the fatty acid may have a degree of unsaturation in the rangeof 0 to 6 per fatty acid molecule. The fatty acid may be of variouslengths and may have 2 to 22 carbon atoms per molecule. Fatty acidderivatives are hydrophobic in nature, and thus can be incorporated intocirculating lipoproteins or cell membranes as a long-lived drug depotfor sesamol. Examples of suitable fatty acids include, but are notlimited to, palmitic acid, oleic acid, linoleic acid, alpha-linolenicacid, arachidic acid, gadoleic acid, 5,8,11,14,17-eicosapentaenoic acid,and 4,7,10,13,16,19-docosahexaenoic acid. Fatty acid derivatives ofsesamol may be synthesized using standard organic chemistry via theactivation of the carboxylic group with an acid chloride, an acidanhydride, or other activating agents such as 1,1 carbonyl diimidazole(CDI).

In alternative embodiments, a hydrophilic derivative of sesamol may beprepared by attaching a carboxylic acid derivative of polyethylene oxideto the sesamol molecule. As used herein, “a carboxylic acid derivativeof polyethylene oxide” refers to a polymer of ethylene oxide with 2 to400 repeating units having at least one of the two hydroxyl terminalgroups converted into a carboxylic acid group. The other hydroxylterminal group may remain underivatized or may be modified. Forinstance, the other terminal group may be methoxylated or converted intoa second carboxylic acid group. The process of attaching one or morechains of polyethylene oxide to a compound is often referred to as“pegylation.” In this case, the attachment of the hydrophilicpolyethylene oxide moiety helps to increase the lifetime of the sesamolcompound in the plasma compartment, which after the derivatization actsas a circulating depot. As the pegylated sesamol circulates in theplasma, sesamol is being slowly released into the system, which helps toreduce its toxicity.

The sesamol derivative may be delivered through traditional methods ofadministration such as via the enteral or various parenteral routes. Forenteral administration, a composition comprising the sesamol derivativemay be formulated into a pill, a soft gelatin capsule, or other methodsknown to those skilled in the art with or without other carriers,excipients, or diluents. Supplementary active ingredients also may beincorporated into the composition. In preferred embodiments, thecomposition comprising the sesamol derivative may be formulated into asoft gelatin capsule with an appropriate oil (e.g., fish oil).Parenteral administration may be through intravenous or subcutaneousinjections. For a sesamol derivative comprising polyethylene oxide, thecomposition may be prepared as an aqueous solution, whereas if a fattyacid is used to derivatize the sesamol compound, the composition may beprepared as an emulsion, a liposome, or a micellar formation. Thesesamol derivative may be delivered neat or may be combined with otherpharmaceuticals or natural products (e.g., fish oil) that also haveanti-inflammatory benefits.

In other embodiments, the composition of the invention may be consumedas a food product, for example, as a nutritional supplement. Preferably,the food product comprises between about 1 gram and about 60 grams ofcarbohydrate and between about 1 gram and about 40 grams of protein.More preferably, both protein and carbohydrate are present in the foodproduct at a ratio of between about 0.5 and about 1.0 of protein tocarbohydrate, inclusive. This ratio helps to lower secretion of insulin,thus reducing the activating impact that insulin has on D5D activity.Food products of the invention may be prepared in various formsincluding, but not limited to, a food bar, a confection product (e.g.,an ice cream), a beverage (e.g., a ready-to-drink mix), a conveniencefood (e.g., a frozen meal), and a stabilized meal.

The following examples are provided to illustrate further and tofacilitate the understanding of the invention and are not intended tolimit the invention.

EXAMPLE 1 Acylated Sesamol Derivatives

Fatty acid is activated using a 1:1 molar amount of 1,1 carbonyldiimidazole in a dry benzene solution. The solution is taken to drynessat the completion of the activation. To the dried compound is added anequimolar amount of sesamol. The combined reactants are heated undervacuum at a low temperature for 1-2 hours. The completeness of thereaction is determined by thin layer chromatography. The acylatedsesamol is then isolated by column chromatography to yield the isolatedinvention. The physical state of the invention depends on the chainlength of the fatty acid and its degree of unsaturation.

EXAMPLE 2 Preparation of Sesamol Oleate

17.7 mmoles of oleic acid was dissolved in 40 ml of dry benzene. To themixture was added 17.7 mmoles of 1,1 carbonyldiimidazole. The reactionto activate the oleic acid was continued at room temperature untilvigorous evolution of carbon monoxide has ceased. The reaction was thendriven to completion by driving off the excess benzene under vacuum at60° C. To the neat activated oleic acid was added 21 mmoles of sesamol.The mixture was heated at 60° C. for 2 hours under vacuum with constantrotation. The crude reaction mixture was purified using 50 grams ofsilica gel 60 in 2×44 cm column eluting with hexane and increasingpercentages of acetone. The fractions containing the active compoundwere collected and evaporated to dryness giving 10 mmoles of the sesamololeate for a 56% yield. HPLC chromatography using a 98:2cyclohexanone/isopropyl eluting solvent give a single component withgreater than 90% purity.

EXAMPLE 3 Polyethylene Oxide Sesamol Derivatives

Methoxy polyethylene oxide molecules of various chain lengths areoxidized by KMnO4 to yield a carboxylic acid derivative. The carboxylicacid derivative of methoxy polyethylene oxide is activated using a 1:1molar amount of 1,1 carbonyl diimidazole in a dry benzene solution. Thesolution is taken to dryness at the completion of the activation. To thedried compound is added an equimolar amount of sesamol. The combinedreactants are heated under vacuum at a low temperature for 1-2 hours.The completeness of the reaction is determined by thin layerchromatography. The acylated sesamol is then isolated by columnchromatography to yield the isolated invention. The physical state ofthe invention depends on the chain length of the methoxy polyethyleneoxide molecule.

Variations, modifications, and other implementations of what isdescribed herein will be occur to those of ordinary skill in the artwithout departing from the spirit and the essential characteristics ofthe invention. Accordingly, the scope of the invention is to be definednot by the preceding illustrative description but instead by thefollowing claims, and all changes that come within the meaning and rangeof equivalency of the claims are intended to be embraced therein.

1. A method for inhibiting the formation of arachidonic acid in a mammalcomprising administering to a mammal a composition comprising anon-toxic derivative of sesamol.
 2. The method of claim 1 wherein thenon-toxic derivative comprises at least one fatty acid.
 3. The method ofclaim 2 wherein the at least one fatty acid comprises 2 to 22 carbonatoms.
 4. The method of claim 2 wherein the degree of unsaturation ofthe at least one fatty acid ranges from 0 to
 6. 5. The method of claim 2wherein the at least one fatty acid is selected from the groupconsisting of palmitic acid, oleic acid, linoleic acid, alpha-linolenicacid, arachidic acid, gadoleic acid, 5,8,11,14,17-eicosapentaenoic acid,and 4,7,10,13,16,19-docosahexaenoic acid.
 6. The method of claim 2wherein the non-toxic derivative comprises sesamol oleate.
 7. The methodof claim 1 wherein the non-toxic derivative comprises a carboxylic acidderivative of polyethylene oxide.
 8. The method of claim 7 wherein thecarboxylic acid derivative of polyethylene oxide comprises 2 to 400repeating units.
 9. The method of claim 1 wherein the composition isprepared as a nutritional supplement in a form selected from the groupconsisting of a capsule, a bar, a tablet, a powder, and a beveragepackage.
 10. A method for moderating an inflammatory response in amammal comprising administering to a mammal a composition comprising anon-toxic derivative of sesamol.
 11. The method of claim 10 wherein theadministering step is carried out enternally or parenternally.
 12. Themethod of claim 10 wherein the composition is prepared as a nutritionalsupplement in a form selected from the group consisting of a capsule, abar, a tablet, a powder, and a beverage package.